The present invention relates, in general, to electronics and, more particularly, to methods of forming semiconductor devices and structure.
In the past, the electronics industry used Light Emitting Diodes (LEDs) for a variety of applications. Improvements in the quality and efficiency of LEDs facilitated the use of LEDs in automotive lighting applications such as for brake lights and taillights. Further advances in LEDs facilitated the use for more traditional AC lighting applications such as traffic lights, fluorescent lights, street lights and other lighting applications. Typical control systems for LED applications converted an AC waveform into a DC voltage and used this DC voltage to power the LEDs. Systems to control LEDs are disclosed in U.S. Pat. No. 6,285,139 issued to Mohamed Ghanem on Sep. 4, 2001 and U.S. Pat. No. 6,989,807 issued to Johnson Chiang on Jan. 24, 2006. Most such LED control systems had a high cost. Other systems to control LEDs are disclosed in U.S. Pat. Nos. 6,038,016, 6,150,774, and 6,806,659 issued to Mueller et al. on Jan. 18, 2000, Nov. 21, 2000, and Oct. 19, 2004, respectively.
Accordingly, it would be advantageous to have a method and circuit for driving one or more LEDs. In addition, it is desirable for the method and circuit to be cost and time efficient to implement.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference characters in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current flow through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-channel devices, or certain N-type of P-type doped regions, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with embodiments of the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action. The use of the word approximately or substantially means that a value of an element has a parameter that is expected to be very close to a stated value or position. However, as is well known in the art there are always minor variances that prevent the values or positions from being exactly as stated. It is well established in the art that variances of up to about ten percent (10%) (and up to twenty percent (20%) for semiconductor doping concentrations) are regarded as reasonable variances from the ideal goal of exactly as described.